JPH0652566B2 - Magnetic recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording medium, particularly to a magnetic recording medium suitable for high-density recording and having improved running durability.

[Conventional technology]

In the magnetic recording medium for high-density recording, which has been developed in recent years, it is required that the surface property of the magnetic layer be higher in order to reduce so-called gap loss between the magnetic head and the magnetic tape. To be done. For this purpose, it is necessary to improve the surface property of the magnetic layer by improving the manufacturing technology of the magnetic layer, that is, improving the dispersion, coating, surface molding technology of magnetic particles, etc. Improvements are also needed. In particular, attempts have been made to reduce the thickness of the magnetic layer in order to escape the thickness loss as the recording wavelength becomes smaller as the recording density becomes higher. As a result, the influence of the surface property of the support on the surface property of the magnetic layer is becoming more and more significant.

Recently, in order to realize higher density recording, Co-Ni, Co-Cr, Fe have been formed by vapor deposition, sputtering, etc.
Although magnetic recording media provided with a ferromagnetic metal thin film such as -N are being developed, the above problem is further increased because the magnetic layer is much thinner than the coating type magnetic layer.

However, improving the surface properties of the support used for the magnetic recording medium is limited for the following reasons. That is, in the step of forming a film and winding it, if the surface property of the film is good, the frictional resistance with respect to the transport roller becomes large, and often meandering or wrinkling occurs. Further, the frictional resistance between the films increases, and the shape of the take-up roll may be distorted.

Various attempts have been made to solve the contradictory problems of the first half. For example, JP-A-53-10
9605 describes a method in which fine particles of a thermoplastic resin are projected on a support and then dissolved and removed with a solvent to form a magnetic layer on the surface.

Japanese Patent Publication No. 46-14555 describes a method in which a polymer solution such as polyamide or polyester is applied on a support and dried to form fine wrinkles, and a magnetic layer is formed on the surface thereof. In Japanese Patent Publication No. 47-6117, polyester or the like is used as a polymer to be coated on a support, and in Japanese Patent Publication No. 38001/1975, thermoplastic polyester or the like is used, and the surface is the same as in Japanese Patent Publication No. 46-14555. There is described a method of forming fine wrinkles on the surface and forming a magnetic layer on the surface thereof.

However, none of the above-mentioned four methods can stably provide satisfactory characteristics as a magnetic recording medium for high-density recording.

In order to solve the above problems, the present applicant has previously provided a non-magnetic layer containing a compound capable of being polymerized by radiation and fine particles on a support, and a magnetic layer provided with a magnetic layer in an undercoat layer irradiated with ultraviolet rays. A recording medium has been proposed (JP-A-60-251510).
Issue).

[Problems to be solved by the invention]

Although the above proposal showed a considerable improvement in the surface property and durability of the magnetic layer, its running durability was not sufficient, and the heat resistance of the support provided with the undercoat layer (nonmagnetic layer) was not improved. There is a problem, especially when a metal thin film is formed on both sides of the support by vapor deposition, sputtering, etc., an undercoat layer is formed on both sides, and when a magnetic layer is provided on one side by vapor deposition, sputtering, etc. The problem is that the layer sticks to the surface of the substrate or can. Further, this problem also occurs in the undercoat layer (nonmagnetic layer) of the back surface when the magnetic layer is provided on both sides by coating and the surface of the magnetic layer is dried and then surface-treated with a calender roll.

Therefore, an object of the present invention is to provide a magnetic recording medium having improved running durability.

Another object of the present invention is to improve the heat distortion resistance of the support and to provide an undercoat layer which does not stick to a substrate or roll when magnetic layers are provided on both sides of the support.

[Means for solving problems]

In order to achieve the above-mentioned object, the inventors of the present invention have conducted various studies on a compound capable of being polymerized by radiation in an undercoat layer (nonmagnetic layer) and fine particles, and as the compound, a (meth) acrylate having a triazine ring. As compounds and fine particles,
It has been found that the purpose can be achieved by using fine particles of silica (SiO ₂ ) having a diameter of 18 to 1000 mμ.
However, when silica is used as solid particles, it is difficult to disperse, and it is difficult or extremely time-consuming to prepare a coating solution. However, when it is used in the state of silica sol, it can be uniformly distributed in a short time. The present invention has been achieved by finding that the above can be achieved.

That is, the present invention provides a non-magnetic layer containing a binder and fine particles between the non-magnetic support and the magnetic layer, and the non-magnetic layer is irradiated with radiation in a magnetic recording medium,
The magnetic recording medium is characterized in that the fine particles are fine particles introduced from silica sol and 45% by weight or more of the binder is a (meth) acrylate compound having a triazine ring.

Hereinafter, the present invention will be described in detail.

As described below, the present invention is preferably applied to a ferromagnetic gold-side thin film magnetic recording medium by vapor deposition, sputtering, etc., but can also be applied to a coating type magnetic recording medium.

Among the binders used in the non-magnetic layer (undercoat layer) of the present invention, the compound polymerizable by irradiation with radiation is a (meth) acrylate compound containing a triazine ring.
Tris (2-acryloyloxyethyl) incyanurate, Is preferred.

The amount of the above compound added is 45% by weight or more, preferably 70% by weight or more, based on the total amount of the binder. If it is less than 45% by weight, sticking tends to occur after coating and sufficient running durability cannot be obtained.

The above compounds may be used alone or in combination of two or more, and also other copolymerizable compounds such as urethane (meth)
Acrylate, oligoester (meth) acrylate, epoxy (meth) acrylate, styrene, vinyl chloride,
Vinylidene chloride diethylene glycol diacrylate,
It can be used together with hexamethylene acrylate.

The radiation-polymerizable compound used in the present invention can be used together with other binders. Examples of these binders include vinyl chloride-vinyl acetate copolymers, cellulose resins, acetal resins, and vinyl chlorides. A thermoplastic resin such as vinylidene-based resin, urethane resin, or acrylonitrile-butadiene resin, which is used as a binder for conventional magnetic recording media, can be used.

As the fine particles used in the present invention, silica fine particles introduced from silica sol (here, silica sol refers to a dispersion of amorphous silicic acid anhydride (silica) fine particles in an organic solvent). The silica particles have a diameter of 18 to 1000 mμ, preferably 30 to 160 mμ. Such fine silica is difficult to disperse in a binder coating solution as a solid powder as described above, but silica sol such as a dispersion in methanol, isopropyl alcohol, toluene, etc. (for example, trade name “OSC
AL ”, manufactured by Catalyst Kasei Kogyo Co., Ltd., has good dispersibility and a uniform coating solution can be obtained. After coating as an undercoat layer (non-magnetic layer) and drying to remove the solvent, silica fine particles are uniformly dispersed (in the present invention, such fine particles are referred to as fine particles introduced from silica sol).

The content of fine silica powder (dried) in the non-magnetic layer is 0.04 to 20% by weight, preferably 1 to 12% by weight based on the total amount of the binder.

In the present invention, the above binder and silica sol are dispersed and prepared by using an organic solvent, and applied on a support.

As the organic solvent used in the dispersion, preparation, and coating of the present invention, acetone, methyl ethyl kentone, and
Methyl isobutyl ketone, cyclohexanone, isophorone, tetrahydrofuran and other ketones; methanol, ethanol, propanol, butanol, isobutyl alcohol, isopropyl alcohol, methyl cyclohexanol and other alcohols; methyl acetate, ethyl acetate,
Ester systems such as butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycol monoethyl ether acetate; ether systems such as diethyl ether, tetrahydrofuran, glycol dimethyl ether, glycol monoethyl ether, dioxane; benzene, toluene, xylene, cresol, Tar-based (aromatic hydrocarbons) such as chlorobenzene and styrene; methylene chloride, ethylene chloride, carbon tetrachloride, chloroform,
Chlorinated hydrocarbons such as ethylene chlorohydrin and dichlorobenzene, N, N-dimethylformaldehyde, and hexane can be used.

Examples of the material for the support of the present invention include polyesters such as polyethylene terephthalate, polyethylene-2, and 6-naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate; polycarbonates, polyimides, plastics such as polyamideimides; Further, aluminum, an alloy thereof, copper, glass, ceramics or the like is used.

After coating the non-magnetic layer on the support as described above, dried,
Then, the compound is polymerized by irradiation with radiation.

As the radiation, an electron beam from an electron beam accelerator or ultraviolet rays can be used.

As the electron beam accelerator, a scanning method, a double scanning method, a curtain beam method or a broad beam curtain method can be adopted.

As electron beam characteristics, the acceleration voltage is 100 to 1000 kV, preferably 150 to 300 kV, and the absorbed dose is 1.0 to 2 megarads, preferably 2 to 10 megarads. When the accelerating voltage is 100 kV or less, the energy transmission amount is insufficient, and when the accelerating voltage exceeds 1000 kV, the energy efficiency used for polymerization is reduced, which is not economical. If the absorbed dose is 1.0 megarad or less, the curing reaction is insufficient and the strength of the non-magnetic layer cannot be obtained. If the absorbed dose is 20 megarads or more, the energy efficiency used for curing is lowered, or the irradiated object generates heat. In particular, the plastic support is deformed, which is not preferable.

When ultraviolet rays are used as the radiation, aromatic ketones such as acetophenone, benzophenone, benzoin ethyl ether, benzyl methyl ketal, and benzyl ethyl ketal are added as photopolymerization initiators. The addition amount is 1 to 10% by weight with respect to the binder.

A mercury lamp is used as the ultraviolet light source. 2 mercury lamps
Using a lamp of 0-200W / cm, speed 0.3m / min.
Used at 20 m / min. Generally, the distance between the substrate and the mercury lamp is preferably 1 to 30 cm.

On the non-magnetic layer formed as described above, a magnetic layer made of a strong magnetic metal thin film is provided by vapor deposition, sputtering or the like, or a magnetic layer dispersed in a ferromagnetic fine powder binder is applied.

The method of forming the magnetic metal thin film applied to the present invention may be a method of forming a film in a vacuum chamber or a plating method, which has a high formation speed of the metal thin film, a simple manufacturing process, or a drainage method. A method of forming a film in a vacuum chamber, which has advantages such as not requiring treatment, is preferable. The method of forming in a vacuum chamber is a method of depositing a substance or a compound thereof to be deposited in a dilute gas or a vacuum space as vapor or ionized vapor on a support which is a base, vacuum vapor deposition method, sputtering method. The ion plating method, the chemical vapor deposition method, etc. correspond to this.

Further, in the present invention, as the ferromagnetic metal layer to be the magnetic recording layer, iron, cobalt, nickel and other ferromagnetic metals or Fe--Co, Fe--Ni, Co--Ni, Fe--
Si, Fe-Rh, Co-P, Co-B, Co-Si,
Co-V, Co-Y, Co-La, Co-Ce, Co-
Pr, Co-Sm, Co-Pt, Co-Mn, Fe-C
o-Ni, Co-Ni-P, Co-Ni-B, Co-N
i-Ag, Co-Ni-Na, Co-Ni-Ce, Co
-Ni-Zn, Co-Ni-Cu, Co-Ni-W, C
A ferromagnetic alloy such as o-Ni-Re or Co-Sm-Cu is formed into a thin film by a method of forming a film in a vacuum chamber or a plating method, and the film thickness is used as a magnetic recording medium. The thickness is in the range of 0.05 μm to 2 μm, and particularly preferably 0.1 μm to 0.4 μm.

As the ferromagnetic powder used in the coating type magnetic layer in the present invention, ferromagnetic iron oxide fine powder, Co-doped ferromagnetic iron oxide fine powder, ferromagnetic chromium dioxide fine powder, ferromagnetic alloy powder barium ferrite, etc. are used. it can. It is effective that the acicular ratio of ferromagnetic iron oxide and chromium dioxide is about 2/1 to 20/1, preferably 5/1 or more and the average length is about 0.2 to 2.0 μm. The ferromagnetic alloy powder has a metal content of 75 wt% or more, and a metal content of 80 wt% or more is a ferromagnetic metal (that is, F
e, Co, Ni, Fe-Co, Fe-Ni, Co-N
i, Fe-Co-Ni) and the major axis is 1.0 μm or less.

As the binder for the magnetic layer, generally used thermoplastic resins, thermosetting resins, reactive resins, or mixtures thereof can be used.

The solvent used for coating these can be appropriately selected and used from the above-mentioned solvents used for coating the nonmagnetic layer.

Further, additives such as a lubricant, an abrasive, a dispersant, an antistatic agent and an anticorrosive agent may be added to the magnetic coating liquid of the present invention.

The non-magnetic layer and the magnetic layer of the present invention may be provided on one side or both sides of the support.

〔Example〕

 Hereinafter, the present invention will be described more specifically.

Example 1 A coating solution having the following formulation was applied and dried on both sides of a polyimide base having a thickness of 50 μm to a dry thickness of 0.7 μm, and UV irradiation was performed on each surface with a mercury lamp of 80 W / cm for 3 times.
It was cured for 2 seconds.

Ingredient (A) Tris (2acryloyloxyethyl) isocyanurate (10% solution of methyl ethyl ketone) X parts by weight (B) Urethane acrylate molecular weight 8000 (10% solution of methyl ethyl ketone) Y parts by weight (C) Silica sol 10% solid content, average particle size Diameter 80mμ Isopropyl alcohol / methyl ethyl ketone (1/1
VoLtt) Z parts by weight (D) Benzylethyl ketal 4 parts by weight For each of the obtained samples # 1 to # 6, a Co-Cr thin film magnetic layer was provided on one of the non-magnetic layers by the following method to test the state of the back surface of the sample adhered to the substrate during sputtering. did.

The back surface having the above-mentioned undercoat layer is brought into close contact with a copper substrate, and the sample is attached and set in a vacuum chamber to obtain 3 × 10 ^−7.
After evacuation to torr, argon was introduced up to 3 × 10 ⁻³ torr. Co-Cr with a power density of 3 W / cm ^{2 by} DC magnetron sputtering while maintaining the substrate temperature at 170 ° C.
The film was provided to a thickness of 2000Å. After forming the magnetic film, the adhesion of the sample to the substrate was examined. Next obtained Co-
50 to 1 perfluoropolyether lubricant on Cr film
After being applied to a thickness of 00Å and dried, it was punched into a 3.5-inch floppy disk and a running durability test was conducted as follows.
That is, recording / reproduction at 600 rpm at 500 Hz was performed on the outermost track. In this case, head pressure 20g, atmosphere 2
It was 3 ° C. and 50% RH.

The obtained results are shown in the following table.

Example 2 The component (A) in Example 1 was changed to the following, and (C)
The components were changed to 4 parts by weight, and the non-magnetic layer was coated on both sides so as to have a dry thickness of 0.7 μm without adding the component (D) and dried.

Next, each surface was irradiated with an electron beam of 5 Mrad at an acceleration voltage of 150 kV and a beam current of 5 mA.

With respect to the obtained sampling, a Co—Cr film was formed by sputtering in the same manner as in Example 1, and the sticking condition and the running durability were investigated.

Example 3 In Example 1, except that the component (A) was changed to the following and the component (C) was changed to 16 parts by weight, the nonmagnetic layer was similarly coated on both surfaces so as to have a dry thickness of 0.7 μm and dried. did.

Then, UV irradiation is performed on each surface as in the example, and Co is applied to one surface.
A -Cr film was similarly provided by sputtering, and the following results were obtained by examining the adhesiveness of the back surface and the running durability of the sample.

[Effects of the Invention] As is clear from the above results, the magnetic recording material provided with the non-magnetic layer (undercoat layer) according to the present invention has excellent running durability, and when a magnetic layer is provided, It can be seen that the undercoat layer does not stick to the substrate or the like, and the thermal deformation resistance of the support is improved.

Claims (1)

[Claims] 1. A magnetic recording medium in which a non-magnetic layer containing a binder and fine particles is provided between a non-magnetic support and a magnetic layer, and the fine particles are made of silica sol in a magnetic recording medium irradiated with radiation. A magnetic recording medium comprising the introduced fine particles and 45% by weight or more of the binder is a (meth) acrylate compound having a triazine ring.